過去在網路外部性的文獻當中，皆忽略對手廠商對個別消費者所產生的網路外部性效果。因此本文主要目的將對手廠商對個別消費者所產生的網路外部性程度大小納入其中，以建立一個結合垂直產品差異化及網路外部性的一般化模型，藉以探討完全覆蓋市場及不完全覆蓋市場之下的市場均衡，並分析Bertrand價格競爭及Cournot數量競爭對廠商最適品質的選擇，以及對市場均衡所造成的影響，最後比較這種兩種競爭模式下均衡結果的異同。由於交叉網路外部性的存在，我們得到與張瑞雲與徐士勛（2009）不同結論：1.相較高品質廠商，低品質廠商在Bertrand價格競爭下具有數量優勢；2.相較低品質廠商，高品質廠商在Cournot數量競爭下可能不具有高利潤優勢，須視自身網路外部性程度大小而定；3.高品質廠商的均衡價格與低品質廠商的均衡數量在Bertrand價格競爭下皆大於Cournot數量競爭下的結果。我們亦發現在Bertrand價格競爭(Cournot數量競爭)下，自身網路外部性的存在會擴大(縮小)品質差異性，交叉網路外部性的存在則會縮小(擴大)品質差異性。最後，在給定網路外部性下，生產者剩餘在Bertrand價格競爭下有可能大於Cournot數量競爭下的結果。

The existing researches in the topic of network externalities usually ignore the type of network externalities that competitor firms bring to individual consumers. In this study, we therefore aim at the inclusion of this type of network externalities in a generalized model which combines both the issues of vertical product differentiation and network externalities. The market equilibria under covered and uncovered market in both Betrand price competition and Cournot quantity competition are also analyzed. We then compare the differences between these two kinds of competition in equilibrium.
By including the existence of cross-network externalities, the study contrasts with Chang and Hsu (2009). We find that, under Betrand price competition, the low-quality firm has larger outputs. In Cournot quantity competition, the high-quality firm may not have larger profit, depending on the degree of self-network externalities. Moreover, the equilibrium price of high-quality firm and the equilibrium quantity of low quality-firm are both higher in Bertrand price competition than Cournot quantity competition. We also find that, under Bertrand price competition (Cournot quantity competition), the existence of self-network externalities enlarges (diminishes) the difference of the qualities of the two firms, while the existence of cross-network externalities diminishes (enlarges) the difference of the qualities. In the end, given the network externalities, producer surplus might be larger in Bertrand price competition than in Cournot quantity competition.

謝辭 i
摘要 ii
目錄 iv
表目錄 v
圖目錄 vi
第一章 緒論 1
第一節 研究背景與動機 1
第二節 研究目的 3
第三節 研究架構 3
第二章 文獻回顧 4
第三章 完全覆蓋市場分析 8
第一節 模型基本設定 8
第二節 Bertrand價格競爭之分析 10
第三節 檢定均衡價格的存在性 20
第四章 不完全覆蓋市場分析 21
第一節 模型基本設定 21
第二節 Bertrand價格競爭 23
第三節 Cournot數量競爭 36
第五章 競爭模式的比較 48
第一節 網路外部性有無之比較分析 48
第二節 不同網路外部性程度對市場均衡的影響 49
第三節 網路外部性對社會福利的影響 53
第六章 結論與建議 58

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中文部分
張瑞雲與徐士勛 (2009)，「網路外部性、品質選擇與廠商競爭模式」，2009財經學術研討會。